1. Field of the Invention
The present invention relates to a laser resonator for generating frequency-converted laser radiation, comprising: a laser-active solid-state medium and a wavelength conversion crystal.
2. Background
Laser resonators for the resonator-internal generation of frequency-converted laser radiation typically have a wavelength conversion crystal within the laser resonator, in which wavelength conversion crystal laser radiation generated at a fundamental frequency or wavelength in a laser-active medium is converted into laser radiation having a typically higher frequency. Wavelength conversion crystals used include nonlinear crystals, for example LBO crystals, which produce a frequency conversion from the fundamental frequency to a higher harmonic, e.g. to the second or third harmonic. For a sufficiently high efficiency of the frequency conversion, in this case a high beam intensity is required in the nonlinear crystal.
In order to generate a sufficiently high beam intensity in the wavelength conversion crystal, it is known to design the beam path of the laser resonator such that the wavelength conversion crystal is arranged in the region of a beam waist. In order to generate a beam waist having a minimum beam diameter, it is possible, for example, for the end mirror adjacent to the wavelength conversion crystal to be embodied in a concave fashion, as illustrated in DE 100 03 244 A1. As likewise described therein, the concave end mirror increases the length of the laser resonator, such that the latter cannot be realized in a compact design. Therefore, DE 100 03 244 A1 suggests using a convex end mirror instead of a concave end mirror, in order thereby to shorten the resonator length and additionally to increase the stability of the laser resonator.